Cardinal Tetras are a wonderful freshwater fish that often get overlooked. This species is pretty, easy to care for, and quite peaceful.

However, there are some aspects of their care that are noticeably different than other fish in their family.

This guide will teach you the fundamentals of Cardinal Tetra care, so you’ll be fully prepared once you decide to buy some. You’ll learn things like ideal water parameters, tank mates, diet, size, and even breeding tips!

Species Summary

The Cardinal Tetra (scientific name: Paracheirodon axelrodi) is a stunning freshwater fish that can liven up any aquarium. Known for their bright coloration and relatively lax husbandry needs, these fish do very well in both natural tanks.

Like their similar-looking cousin, the Neon Tetra, Cardinal Tetras are frequently bred in captivity, resulting in large numbers of fish in the trade. In the wild, these fish form groups of hundreds, creating large schools of moving color!

Author Note: Even in small groups, Cardinal Tetras will gather and exhibit some beautiful shoaling behavior.

Cardinal Tetras reside in throughout South America. They’re mostly found in the Orinoco and Negro rivers. Though, their distribution is quite vast.

These fish do very well in captivity. Peaceful by nature, Cardinal Tetras make wonderful additions to community tanks big and small.

Lifespan

The typical Cardinal Tetra lifespan is between four and five years when healthy. 

Author Note: Interestingly enough, these fish are known to live longer in captivity than in the wild. In many areas, they’re believed to be an annual species with a very short lifespan!

When kept in captivity, Cardinal Tetras need stable conditions to live long lives. Failure to address their needs could result in stress, disease, and even premature death.

Appearance

Many people actually mistake Cardinal Tetras for Neon Tetras, and it’s not hard to see why! These two species have very similar appearances.

The Cardinal Tetra is a slender fish with a torpedo-shaped profile. Like the Neon, these fish have two distinct stripes of red and blue.

One Cardinal Tetra swimming in a freshwater aquarium

Running from the tip of the nose to the tail, the blue stripe shimmers in the light. It has an iridescent finish, making it glow in the right lighting conditions.

Directly below the blue stripe is a thicker band of bright red. It runs the entire length of the body and even bleeds into the transparent tail.

The main difference between Cardinal Tetras and Neon Tetras is the length of this stripe. For Neons, the red color only marks half of the body.

All of the fins on the Cardinal Tetra are transparent. The belly is usually white. These fish are very colorful with some unique variations that exist as well (such as gold and silver). However, these colors are very rare.

The physical differences between males and females are very subtle. Typically, females will appear more rounded. This is especially true around breeding season. Meanwhile, males have a small hook accent on their anal fins.

Average Size

The average Cardinal Tetra size is around two inches in length when fully grown. That makes them a rather small freshwater species that can be kept in fairly compact tanks.

Cardinal Tetra Care

Cardinal Tetra Care is pretty easy for the most part. This species is not very fussy and can thrive as long as you keep them in the right conditions.

That said, many aquarists recommend that you have at least a little prior experience caring for fish before you attempt to raise Cardinal Tetras. That’s because they require a very stable environment to stay healthy!

To help you, here are some important care guidelines to follow:

Tank Size

It’s not uncommon to see a couple of Cardinal Tetras living in a small 10-gallon tank. These fish can do well in tanks of that size.

However, we always recommend using an aquarium that can hold at least 20 gallons. If you can go with a larger tank size, that’s even better!

Author Note: Cardinal Tetras love to swim around in groups. Having more open space to foster this behavior is very good for their health and overall quality of life. The fish that live the longest tend to have the most space!

Water Parameters

To give Cardinal Tetras the best life possible, it’s best to replicate their natural habitat when it comes to water parameters. These fish come from slow-moving waters in South America where the environment is warm, clear, and heavily shaded.

Author Note: This isn’t a species that you can just plop into a newly established tank. Water chemistry must be stable before they can be introduced. Give your aquarium some time to cycle and monitor the parameters closely.

The water needs to be slightly acidic and very soft. Too many dissolved minerals in the water could be detrimental to the fish’s health.

Below are the water parameters to aim for.

  • Water temperature: 73°F to 81°F (above 75°F is preferred)
  • pH levels: 5.0 to 7.5 (below 6.0 is ideal)
  • Water hardness: 2 to 6 KH

In order to make sure the parameters are stable and consistent it’s important to perform regular water tests. Get a reliable and accurate test kit and be sure everything is suitable before introducing this species to their new home.

Setting Up The Rest Of Their Tank

Natural decor that mimics their natural habitat is best. These fish can live in all types of environments. However, they’re usually found in shallow rivers and streams surrounded by a ton of vegetation.

Cardinal Tetras stick to the middle of the aquarium, but that doesn’t mean that you can ignore the substrate. Your best option would be fine sand. The sand closely resembles riverbeds and acts as the perfect anchor for live plants.

Two cardinal tetras swimming together near the substrate

Speaking of which, you’ll need a lot of plants! Anubias, Java Fern, and Amazon Swords are all good cultivars to try. Strike a good balance between floating plants and submerged plants.

When arranging the plants, leave an open space in the middle. The vegetation is important for blocking out light and providing shelter, but that open swimming area is crucial, too.

On the bottom of the tank, you can incorporate rocks and driftwood, too. Larger chunks of driftwood work well because they extend to the middle part of the water column where the Cardinal Tetra can use them.

For lighting, keep things relatively subdued. These fish do not like powerful lights and are most comfortable when things are slightly dim.

Potential Diseases

There are a few different diseases that you need to keep an eye out for. These fish are susceptible to common freshwater problems like Ich, dropsy, and fin rot.

The good news is that these diseases are easy to treat with some over-the-counter medications. They’re even easier to prevent with good tank maintenance!

Perform regular water changes and use test kits to analyze the water chemistry. Make sure that your filtration system is in good working order as well to prevent ammonia and nitrate levels from going out of whack.

One unique health issue to be wary of is Neon Tetra Disease. Despite its name, this disease affects a wide range of different types of tetras.

It’s a parasitic disease that’s often brought into tanks through other infected fish or infected live foods. The disease causes spinal issues, cysts, and a load of other health problems. Unfortunately, there is no known cure for it.

Author Note: If you want to play it safe before adding new fish into the mix, quarantine them to ensure that you’re not bringing any diseases into the larger community environment.

Food & Diet

Cardinal Tetras are omnivores that usually feed on worms and small crustaceans in the wild. They are willing to accept a wide variety of foods which makes feeding them easy.

However, these fish do have high vitamin needs!

As a result, about three-quarters of their diet should be dried flakes or pellets. Stick with a balanced food product that’s specifically marketed towards Tetras.

To supplement that food, you can provide live or frozen snacks. Brine shrimp, bloodworms, and other popular high-protein foods are always appreciated. Just make sure that the food is small enough to fit into the Cardinal Tetra’s mouth.

It’s best to feed these fish several times a day if your schedule allows for it. Provide only enough food that they can eat in about three minutes (anything more will result in overfeeding).

Behavior & Temperament

Cardinal Tetras are very docile and peaceful creatures, which makes them easy to care for. They aren’t known to show any signs of aggression in genera!

Author Note: This is something to be mindful of when finding compatible tank mates (more on that in the section below). They’re often the target of bullies due to their peaceful nature.

Being kept with other Cardinal Tetras is very important. When they’re alone, these fish will become shy and stressed. Most will even begin to lose their color.

It’s best to keep Cardinal Tetras in groups of at least six. A larger school will help the fish feel confident and help keep it healthy. Throughout the day, the fish will explore the tank and swim together.

Tank Mates

Beyond other Cardinal Tetras, these fish do well in community tanks. There are many possibilities when it comes to tank mates.

As a good rule of thumb, avoid any fish that’s even slightly aggressive. Territorial species will bully the Cardinal Tetra. These fish are delicate and don’t have much in terms of defense, so it’s best to keep things peaceful.

Also, avoid any larger fish that could eat them (obviously). This applies to peaceful species, too. Sometimes this can happen by mistake!

Some good Cardinal Tetra tank mates to consider include:

Cardinal Tetra Breeding

For a while, Cardinal Tetra breeding posed a big challenge to breeders. While established breeding methods do exist, it’s still a big challenge. You have to get conditions just right to trigger spawning.

Create a separate breeding tank with stable water conditions. Keep the lights low, as fry are very sensitive to light. Add your bonded pair and condition them with live foods.

If you’re successful, the pair will breed during the evening. The female will lay upwards of 500 eggs at once! Typically, the male will swim alongside the female as she distributes the eggs in plants.

Remove the pair immediately after all of the eggs are laid. These fish do not show any parental instincts and will eat the eggs.

It only takes about 24 hours for the eggs to hatch. The fry will survive off of the egg sac for about five days until they can swim freely.

At that point, provide infusoria, powdered fry food, and baby brine shrimp. In about two to three months, the babies will start taking on the same coloration as the adults.

Conclusion

As long as you have the right information, Cardinal Tetra care shouldn’t be too difficult to manage. While we typically recommend that first-time aquarists try another species first, these are are far from an expert-only fish.

We know tons of owners who absolutely love these fish and plan on keeping tanks with them for years to come. Maybe you should do the same!

If you have any other questions about this freshwater species, feel free to get in touch with us directly. We love chatting with our readers and helping them out!

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